1. Statement of the Technical Field
The present invention relates to the field of medical diagnostic imagery and, more particularly, to breast cancer detection systems.
2. Description of the Related Art
Breast cancer is the most common major cancer among women in the United States and breast cancer is the leading cause of cancer deaths in women, second only to lung cancer. An estimated 200,000 cases of breast cancer are diagnosed each year and more 43,300 lives are claimed in consequence. Significantly, in their lifetime, women of all ages have a one in eight chance of developing breast cancer. In consequence, early detection of breast cancer remains paramount to the survivability of victims of breast cancer. Though advances in the treatment of breast cancer have been made, the effectiveness of conventional breast cancer screening methods remains questionable.
Specifically, a decade-long study conducted amongst 260,000 Chinese women in Shanghai concluded that, in general, women examining their breasts remain unable to detect tumors early enough to reduce their risk of dying from breast cancer. To that end, Dr. Susan Love, a breast cancer surgeon, author of the text, “Dr. Susan Love's Breast Book”, and president of the Susan Love Breast Cancer Foundation observed, “[B]y the time you can feel the cancer, it most likely has been present for about six to eight years. If it was going to spread, it has had ample opportunity.”
The use of x-ray mammography for early breast cancer detection has not proven to be the silver bullet of breast cancer detection. In particular, the effectiveness of x-ray mammography has been questioned at all levels. Notably, recent studies show that while x-ray mammography screening in older women can reduce the probability of dying of breast cancer by thirty percent, the reduction is much less for younger women. In this regard, much of problem with x-ray mammography relates to the inability for x-ray mammography to image dense tissue.
Consequently, the results of an x-ray mammography may show suspicious areas where no malignancy exists (up to twenty percent of biopsied growths identified as cancerous by a mammogram are identified as malignancies). Furthermore, radiologists interpreting x-ray mammography imagery can overlook between fifteen and twenty-five percent of cancers. Finally, the current process for conducting x-ray mammography can be severely uncomfortable. Specifically, the use of imaging plates can cause bruising in the breasts and can, therefore, be a significant disincentive for women to undergo mammography screening.
Notably, in the past five years, microwave imagery has formed the basis of a new, alternative detection technique useful in the early detection of breast cancer. Conventional X-ray mammography utilizes high-energy ionizing radiation that is passed through the breast to a photographic plate in order to shadow potential tumors. In contrast, microwave detection utilizes an array of antennae affixed to the breast surface that can “bounce” non-ionizing microwave radiation off malignant growths whose radiation can be detected by the array. Based upon the characteristics of the “bounce” growths can be detected much in the same way that radar can be used to detect objects at a distance.
Not surprisingly, microwave imaging for use in breast cancer detection has been referred to as “breast tumor radar”. In a typical implementation, a computer can be coupled to an array of small antennae beaming 6 GHz pulsed microwaves. As normal breast tissue remains largely transparent to microwave radiation, breast tumors contain more water causing the scattering of the beamed microwaves back toward their source. The antennae can detect the scattered microwaves which can be analyzed to construct a three-dimensional image showing both the location and size of the tumor.
Microwave imaging based upon the water content of the tumor has been used in the applications of both ultrawideband radar technology and confocal optical microscopy. Such applications can exploit the dielectric contrast between normal breast tissue and malignant tumors at microwave frequencies. Specifically, each element in an antenna array can sequentially illuminate an uncompressed breast with a low-power ultrawideband microwave pulse. Following the acquisition of backscattered waveforms, the array can be synthetically focused by time shifting and adding the recorded returns. A subsequent synthetic scan of the focal point permits the detection of strong scattering sites in the breast, which can be identified as malignant tumors.
Nevertheless, confocal microwave imaging techniques for breast cancer detection remain unable to precisely differentiate malignancies from benign tumors, largely due to the imprecise modeling of the breast. More particularly, conventional confocal microwave imaging systems for breast cancer detection rely upon either a planar or cylindrical modeling of the breast. For the planar configuration, the patient can be oriented in a supine position with the breast being modeled as a flat plane having infinite dimensions. By comparison, for the cylindrical configuration, the patient can be oriented in a prone position with breast being modeled as an infinitely long cylinder. Yet, in reality, the shape and size of any given breast can vary from person to person. Moreover, irregularities can persist about the boundary between the breast skin and surrounding tissue and also about the boundary between the breast tissue and the chest wall.